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TIFR Researchers discovery challenges theory of superconductivity

Researchers’ team from Tata Institute of Fundamental Research (TIFR) have discovered that bismuth semi-metal in bulk form becomes a superconductor.

The team was lead by Dr. S. Ramakrishnan of the Department of Condensed Matter Physics and Material Sciences at TIFR, Mumbai. 

What researchers have discovered?

They have discovered that when temperature of bismuth semi-metal in bulk form is lowered to 530 microKelvin (about -273 degree C), it becomes a superconductor. It acts as superconductor at temperature three orders of magnitude higher than the theoretical prediction.

Significance
  • This landmark discovery challenges the conventional understanding of superconductivity based on Bardeen-Cooper-Schrieffer (BCS) theory.
  • It cannot explain the superconductivity seen in bismuth as it only explains superconductivity in most low Tc (critical temperature) superconductors.
  • The discovery demands a new theory and a new mechanism to understand superconductivity in bismuth.
  • It provides an alternative path for discovering new superconducting materials which are very different from the conventional superconductors.
What are Superconductors?

Superconductors are materials that conduct electricity with no resistance whatsoever. In order to achieve superconducting state, the element should have mobile electrons, and these electrons should come together to form pairs, known as Cooper pairs.

Unusual phenomenon in bismuth

Unlike other elements in the periodic table, bismuth has unusual phenomenon. Bismuth has only one mobile electron per 100,000 atoms. Whereas, the metallic superconductors have one mobile electron per atom. Since carrier density of bismuth is so small, it was believed that bismuth will superconduct. Thus, superconductivity in bismuth is puzzling.

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British trio David Thouless, F Duncan M Haldane and Michael Kosterlitz win 2016 Nobel Prize in Physics

British trio of physicists David Thouless, F Duncan M Haldane and Michael Kosterlitz have won the 2016 Nobel Prize in Physics. They will share the 8 million Swedish kronor prize.

The Royal Swedish Academy of Sciences has selected them for their individual researches on theoretical discoveries of topological phase transitions and topological phases of matter.

Key Facts

  • Their research work centres on Topology, a branch of mathematics involving step-wise changes like making a series of holes in an object.
  • For example when matter goes from solid to liquid to gas different phases are obvious, but materials can also undergo topological step changes which affect their electrical properties.
  • Such changes can be seen in a superconductor, which at low temperatures conducts electricity without resistance.
  • These trio physicists had worked in the field of condensed matter physics and have discovered totally unexpected behaviours of solid materials.
  • Based on their individual discoveries they came up with a mathematical framework in the field of topology to explain these weird properties.
  • The discoveries have paved the way for designing new materials with all sorts of novel properties that have significant potential revolutionize advances in electronics and future quantum computers.

About Awardees

  • David J Thouless: He is Emeritus Professor at the University of Washington, Seattle, US.
  • Duncan M. Haldane: He is the Eugene Higgins Professor of Physics at Princeton University, US.
  • J Michael Kosterlitz: He is the Harrison E. Farnsworth Professor of Physics at Brown University, US.

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Scientists discover new property of light based on Angular Momentum

Scientists from Trinity College Dublin’s School of Physics and CRANN Institute have discovered a new property of light based on Angular Momentum.

The scientific breakthrough discovery has potential to alter the basic understanding of fundamental nature of light.

Key facts

  • The discovery was made by passing light through crystals. During it passage, unexpected new property of light, based on the concept called ‘angular momentum’ was observed.
  • Earlier, physicists always thought that in all forms of light the angular momentum (measures how much a beam of light is rotating) will be a multiple of Planck’s constant (physical constant that sets the scale of quantum effects).
  • But in the new discovery scientists discovered very different behavioural of angular momentum.
  • They found angular momentum of each photon (a particle of visible light) takes only half of this value i.e. each photon have half-integer values of angular momentum.
  • This new property causes a beam of light to be confined to fewer than three dimensions.
  • Significance of Discovery: Help in study of light waves in areas such as secure optical communication which will open up new means for faster internet connections.
  • Enable to study new possibilities including particles whose quantum numbers are fractions of those expected.
  • For the first time the discovery shows how quantum mechanics works for particles that are free to move in only two of the three dimensions of space and can be realised with light.

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